A variety of processes and solutions have heretofore been used or proposed for use to deposit a dark or substantially black nickel deposit on various conductive substrates. Such so-called black nickel deposits are particularly suitable for various decorative purposes as well as to promote absorption of radiant energy such as in solar heating systems, and the like. Typical of such prior art techniques for depositing a black coating or black nickel deposit on metallic substrates are those disclosed in U.S. Pat. Nos. 2,679,475; 2,844,530; 3,127,279; 3,681,211 and 3,753,873.
A continuing problem associated with such prior art techniques has been the difficulty in controlling the composition and process to consistently achieve substantially black coatings which are adherent to the substrate, which provide for improved corrosion resistance, and which are receptive to receiving a clear lacquer or other siccative finish coating.
The problems and disadvantages associated with known prior art techniques are overcome in accordance with the composition and method of the present invention in which the bath composition can be operated over a broad range of pH, concentration, current density and temperature, and is adaptable for use on a variety of different conductive substrates to consistently produce substantially uniform and adherent substantially black nickel deposits which provide improved corrosion resistance and are also receptive to a variety of clear lacquer finish coats.